Unsubscribe using the handle gained from calling #subscribe().
The callback that was sent into the #subscribe() call that you retrieved the
handle from will be unsubscribed from all of the topics subscribed to

observer_obj.unsubscribe(handle)

Unsubscribe by specifying the topics, callback, and context (if one was
when subscribed).
Note: if you use an anonymous in the #subscribe() call, you can retrieve a
reference to the callback from the handle's 'callback' property

Publish to a topic (or topics)
When you publish, you may send data to the subscribers, or you can leave the
parameter empty if you have no particular data to send. The data does not have
a particular format that it must be in, giving you the flexibility to use it
in whatever way is appropriate for your application

Topics can use any name that can also be used as a property name. Since the
topic is always retrieved using the bracket notation (e.g. object["prop"]), as
opposed to the dot notation (e.g. object.prop), you are allowed to use a large
numbers of characters that aren't legal for variable names, such as slashes ("/")
or periods ("."). You cannot, however, use a space (" ") because this is the
character that separates multiple topics.
All three functions (subscribe, unsubscribe, and publish) are able to take one
or multiple topics (separated by a space).

The handle that is returned from the #subscribe() function is simply an object
with three properties, named "topics", "callback", and "context" that correspond
to the three parameters that you sent in (or context will be a blank object if
no context was provided):

handle =
topics : "the topics you sent in"
callback : (topic, data)->
// this is the callback function you sent in
context : contextObjYouSentIn || {}

The first argument that the callback receives is the topic in which the
function was subscribed and invoked from. This will always be a string
containing only one topic, even if the #publish() function is called with
multiple topics because the callback will be run once for each individual
topic that is published.